I upgraded my friends Powerbook G4 15" 1.6 GHz to leopard from tiger. but me being unaware that pro tools is not compatible with leopard. it just won't start up. and also a app called reason shows a "MIDI Failed" message and then quits. also garageband doesn't want to launch. and in the dock, about every 10 seconds a folder pops up and starts bouncing and its title is "MIDI" and some more words that i don't remember. so he asked me if i could downgrade him back to tiger. but i don't know how to do a restore. i DON'T what to erase his HD, i just want to reinstall the operating system. How do i do this? and he can't find his Powerbook Restore disks, so would a regular tiger install disk work? would other powerbook restore disks work? and would this RESOLVE THE PROBLEM??????? if not, what will? PLEASE, PLEASE, PLEASE HELP!!!